Patent Literature 1 shows in FIG. 4 (FIG. 6 in the present description) and in FIG. 8 (FIG. 7 in the present description) a known steam selector. The steam selector is roughly composed of a module body (33), a valve spindle (86), a valve body (58), and a piston (59).
In such a switching valve, the valve spindle (86) is moved up and down by the piston (59). When the valve spindle (86) is pushed down, a seal plug (99) disposed in the valve element formed at the lower portion of the valve spindle comes into close contact with a front-side valve seat (104) of a left-side valve to enter a closed state in which a fluid cannot get into a fluid control chamber (50). When the valve spindle (86) is pushed up, a back-side seal plug (98) comes into close contact with a back-side valve seat to enter an open state in which a fluid inside the fluid control chamber (50) is sent to the control chamber (50) on the right, passes through a flow passage (26), and is discharged outside the switching valve.
Arranging multiple steam selectors with such a structure and sending a large number of types of gases being switched swiftly to an analysis device allow an efficient analysis.